The Army Goes Green

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Oct 30, 2009

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The Heavy Expanded Mobility Tactical Truck (HEMTT) is the Army's workhorse truck, used in a wide variety of configurations to transport materials and equipment. But with an average fuel economy of three to four miles per diesel gallon, these behemoths are thirsty. Oshkosh, a leader in next-generation hybrid propulsion systems, is hoping to change that.

The company is testing a fuel-efficient and environmentally-more-friendly diesel-hybrid, the HEMTT A3, which promises to cut fuel consumption by up to 20 percent—for an average of four to five miles per gallon—enough to save the Army a small fortune in fuel costs. But a heavy-duty, military grade truck needs something beefier than an upscaled Prius drive train, so Oshkosh developed what it calls ProPulse technology: A diesel engine powers an electric generator, which then powers motors mounted directly to the wheels, powering the vehicle in much the same way as a diesel-electric locomotive.

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"This diesel-electric hybrid is like nothing on the road today," says Oshkosh's Joaquin Salas. "We've taken a completely different approach from just mounting batteries on a standard chassis."

In fact, the truck uses no batteries at all. Instead, ultra-capacitors store energy created by regenerative braking, and then deliver power to the wheels during acceleration. The A3 can also act as a generator, delivering 200 kilowatts of AC power for external operations.

"The truck can pull right up and supply power to a field hospital or a command and control unit," Salas says.
The A3 has already been tested at an airfield, where it was able to power the tower and all the lights on the airstrip. In the aftermath of Hurricane Katrina, an A3 spent a week at Mercy Hospital in New Orleans, powering pumps used to dry the flooded medical facility.

Oshkosh promises a top speed of 65mph on gravel roads. And while the A3 is 3,000 pounds lighter than its predecessors at 35,000 pounds, it can still carry the same amount of cargo, 13 tons.

Low-rate production of the HEMTT A3 is set to begin in 2008, and with future projects already planned for the Marines and other branches, there is no telling how much fuel the ProPulse system could ultimately save on the battlefield. —Ted Latiak

Ted Latiak spent six years in the Army as a Captain with the 10th Mountain Division.